Authors:

Marco FellJ. H. Bilgram(ETH Zurich, Switzerland)

In our experiments we study the influence of transient growth
conditions on the growth of xenon dendrites from undercooled
melt. Here we report on the response of crystal growth on heating
the melt. We start heating at a given temperature and
steady-state growth. The dendrite tip reacts on this change by
slowing down growth rate $v$ and increasing tip radius $R$. We
observe that side branches emerge from an unstable surface. As we
continue heating up to slightly above melting temperature, the
tip radius continuously decreases to a new value. The reverse
temperature change unveils a hysteretic behavior: As soon as we
cool down the melt from a temperature tight above melting
temperature, $v$ and $R$ both increase. The curvature of the tip
becomes too small to be stable at the given undercooling and an
instability leads to a new, thin tip growing out of the oversized
sphere-like tip. The value $R^2v$ shows a sharp peak and then
settles to a constant value in only about 20 seconds. The same
instability also gives rise to side branches whose formation can
be controlled by a repetitive application of the described
mechanisms. Highly symmetric xenon crystals can be grown by this
technique.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2006.MAR.A8.5